Ivermectin has been shown in trials in both South India and elsewhere to be very effective in clearing microfilaremia in patients with bancroftian filariasis. Current studies in South India and Brazil (coordinated with trials elsewhere in the world) are focused on developing a regimen to optimize the duration of microfilarial clearance. Recent investigation has indicated that the Tropical Pulmonary Eosinophilia syndrome can be caused by nonfilarial parasites as well as by filariae. Work to differentiate these two pulmonary eosinophilic conditions and develop appropriate therapy is underway using tools of molecular characterization. Loiasis in expatriate visitors to endemic areas has been characterized as having marked clinical and immunologic hyperresponsiveness to the filarial parasite; predictors of relapse and response to definitive therapy have been analyzed and found only to relate to the strain of infective parasite. Because standard therapy for loiasis in heavily infected individuals is quite dangerous, a trial of albendazole for loiasis has been completed and appears to be safe and efficacious.